<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <style>
        *{
            list-style: none;
            box-sizing: border-box;
            margin: 0;
            padding:0;
        }
        html,body{
            height: 100%;
            width: 100%;
            padding-top: 100px;
            display: flex;
            justify-content: center;
        }
        ul{
            background-color: rgb(255, 255, 255);
            border:2px solid black;
            height: 100px;
            width: 100px;
            padding:0;
            overflow: hidden;
            height: 25px;
            
        }
        ul:hover{
            height: 100px;
        }
        li{
            height: 25px;
            width: 100%;
            text-align: center;
            line-height: 22px;
        }
        .inner{
            background-color: rgb(225, 130, 130);
        }
        .inner:hover{
            background-color: blue;
            color:white;
            cursor: pointer;
        }
    </style>
    <title>Document</title>
</head>
<body>
    <ul>
        <li>点我选择</li>
        <li class="inner">首页</li>
        <li class="inner">内容</li>
        <li class="inner">我的</li>
    </ul>
</body>
</html>